Method and means for truing chaser bars



Judy 24, 11923. 1,4627% c. JOBST METHOD AND MEANS FOR TRUING CHASER BARS Filed Jan. 10 1921 INYEN T UR wag/v Patented July 24, i923.

Parana carton.

CON JOBSHL OF TOLEDO, OHId, ASSIG IVOR TO ROBERT L. ELLERY, F TOLEDO, OHIO.

METHOD KND MEANS FOR IRVING CHASER 13A.

Application filed January 10, 1921. serial Ito. 436,080.

To all whom it concern;

Be it known that I, CONRAD J OBST, a citizen of the United States, and a resident of Toledo, county of Lucas, and State of Ohio, have made an Invention Appertaining to Methods and .Means for Truing Chaser Bars; and I do hereby declare the following to be a full, clear, and exact description ofthe invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to the characters of reference marked thereon,

I which form a part of this specification.

This invention relates to truing means for thread cutting chasers for use particularly when accurate work is desired.

It is found in practice, in the manufacture of chasers for thread cutting purposes, that upon hardening a chaser, after cutting threads thereon, a certain amount of distorting or warping of the chaser always takes place so that it is necessary to true the chaser before'cutting a thread. therewith to prevent error in the cut thread.

'The object of my invention is the provision of a simple method and means for truing chasers preparatory to Tusin the 1 same, whereby a true and accurate t read ma be cut thereby. I l he invention is fully described in the fol-' lowing specification, and while, in its broader aspect, it is capable of embodiment lIl'IlUlIlBiOllS forms, a preferred embodiment thereof is illustrated in the accompanying drawings, in which,- I

Figure 1 is a side elevation of an apparatus embodying the invention with parts thereof broken away and with a set of chasersmounted in truing position thereon. Fig. 2 is a top plan view of the chaser holder of the apparatus with chasers held in truing position thereby, and Fig. 3 is an enlarged a number of longitudinally extending threaded ribs or projections 6 corresponding tothe number of chasers to be trued, four being shown in the present instance.

A plurality of standards'7, four in the present instance, rise from the holder base In equidistantly spaced circular order around the thread gauge 5, and each has a chaser clamping face offset in the same direction, circularly of the gauge, from respect1V6 I'fl-dll thereof, so that suchface is tangential to a circle struck around the gauge axis. A clamping member 8 is secured to the clamping face of each standard 7 by a screw 9, or in any other suitable manner, and cooperates with the standard to clamp a chaser 10 thereto with the longitudinal l ne of the chaser in register with a radius llne of the gauge axis, as shown by the line a in Fig. 2 and with its cutting nose in enga ement with the gauge thread.

11 practicing the invention, each chaser 10 of a set, after being tempered, is placed between a respective standard 7 and clamp 8 with the edge thereof to be trued projecting above the top plane of the standard and of the gauge 5. The chaser is then pushed inward against the gau e 5 with its thread fitting perfectly with t e gauge thread, and is'then clamped rigidly in such position to the standard by a tightening of the screw 9. This having been done with all the chasers of a set, the holder is clamped to a table 2 by magnetism, or in any other suitable manner, and moved backward and forward by a movement of the table under a wheel or other grinding medium 11 by which the exposed upwardly projecting edges of the chasersare ground to true form. The trued surfaces of the chasers are the surfaces which are intended to bear against the trued chaser coacting surfaces of a die carrying head.

It is preferable to reduce the point of engagement of a chaser with the gauge thread as much as possible so that the chaser may be more easily and accurately squared therewith, and for this reason the threaded end of each chaser is intended to lap only a restricted edge portion of a threaded rib 6 of the gauge 5 so that only the point or end edge of one is in engagement with the point or side edge of the other.

To further facilitate a perfect and accurate matching of the gauge and chaser threads when one is placed in contact with not limited to any specific construction, ar-

ranger'hent, or form of the parts, or to any specific method of practicing the. same, 8X1

cept in so far as such limitations are specified in the claims.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent,-'

1. The method of truing a thread cutting chaser bar, which consists in placing the threaded end of a chaser in true interfitting engagement with the thread of a gauge part, then securing the bar in rigid relation to the gauge part, and then acting on an exposed part of the chaser bar to true the same.

2. A device of the class described, comprising a holder, a master thread gauge fixed to the holder, and means for clamping a thread cutting chaser bar to the holder with its threaded end in true engagement with the gauge thread and with a surface disposed in position to be trued.

3. In a device of the class described, a holder having a plurality of standards arranged around a central point, a threaded gauge stud fixed to the holder in central relation to the standards, and means for clamping a chaser bar to each standard with the threaded end of the bar in true interfitting engagement with the gauge stud thread and with a surface thereof in position to be trued.

4. In an apparatus of the class described, a holder having a threaded gaugestud rising therefrom, and means parried by the holder at spaced intervals around the stud for holding. a plurality of chaser bars in rigid relation to the stud with their threaded ends in true interfitting engagement with the stud thread.

5.'In a device of the class described, a stud having a threaded gauge rib extending longitudinally thereof, and means for rigidly holding a chaser bar with its threaded end in true interfitting engagement with the gauge thread, and only slightly overlapping the rib edge. v

6. In a device of the class described, a member having a gauge thread with the thread. groove enlarged, at opposite sides of the pitch line whereby the thread of a work-piece placed in engagement with the gauge thread will have coaction only with the pitch portion of the, gauge thread helix.

In testimony whereof I have hereunto signed my name to this specification.

CUNRAD JOBST. 

